Apparatus for carrying and loading top-rollers in a drawing machine

ABSTRACT

Apparatus for carrying and loading top rollers comprising a carrier arm and an operating lever movable about a fixed shaft. The carrier arm and the lever are interconnected for movement about the shaft. A second fixed point or shaft is provided which cooperates with the first shaft to convert the pivoting movement of the carrier arm into an upward movement, creating a partial load position in addition to a closed and open position.

United States Patent [1 1 Dausch et al.

[ APPARATUS FOR CARRYING AND LOADING TOP-ROLLERS IN A DRAWING MACHINE [75] Inventors: Ernst Dausch, Stuttgart; Friedrich Kubler, Ludwigsburg; Theodor Hempel, Stuttgart-Weilimdorf; Franz Fuchs, Magstadt, all of Germany [73] Assignee: SKF Kugellagerfabriken GmbH,

Schweinfurt, Germany [22] Filed: Apr. 21, 1971 [21] Appl. No.1 135,869

[30] Foreign Application Priority Data Apr. 22, 1970 Germany 2019352 [52] US. Cl. 19/267 [51] Int. Cl D01h 5/46 [58] Field of Search 19/266, 267, 295, 272

[ Jan. 29, 1974 [56] References Cited UNITED STATES PATENTS 3,044,128 7/1962 Gerber 19/295 FOREIGN PATENTS OR APPLICATIONS l,l35,350 8/1962 Germany 19/295 Primary Examiner-Dorsey Newton Attorney, Agent, or FirmRichard Low; Murray Schaffer [5 7 ABSTRACT Apparatus for carrying and loading top rollers comprising a carrier arm and an operating lever movable about a fixed shaft. The carrier arm and the lever are interconnected for movement about the shaft. A second fixed point or shaft is provided which cooperates with the first shaft to convert the pivoting movement of the carrier arm into an upward movement, creating a partial load position in addition to a closed and open position.

7 Claims, 7 Drawing Figures mimiumzs m4 3.787.933

sum 1 [1F 6 Fig.1

Fig. 2

ERNST DfiyscH FRIEDRICH K BLE THEopaR #EmPEL FRAIUL cIHS IN VEN TORQ Pmmm 3.781.933

SHEET 2 [IF 6 RA/ST "DHuscH FWEMMH KJBLER THEOPOR HEMFSL RANZ FU H INVENTORS BY/ 9% Wm APPARATUS FOR CARRYING AND LOADING TOP-ROLLERS IN A DRAWING MACHINE BACKGROUND OF INVENTION The present invention relates to yarn spinning and drawing mechanisms and in particular to apparatus for carrying and loading top-rollers therefor.

Conventional spinning and drawing machines include a plurality of top and bottom rollers aligned along a longitudinal plane through which the slivers of fibers are drawn and twisted into a yarn. The top rollers are mounted in linkages secured on a pivotal carrier which is manipulated via an operating lever so that the top rollers can be moved into and out of engagement with the bottom rollers. In the German patent publication DAS 1,162,240 the construction is shown wherein the carrier arm is pivotally supported on a stationary pin fixed in a housing while the operating lever is provided with a forked or bifurcated end and is itself pivoted at the end of the carrier arm. A lug, acting as a pressure linkage is fixed to the carrier arm and interposed between it and the operating lever so that on rotation of the operating lever the carrier arm is caused to pivot. This device is capable of obtaining well defined position either in the closed or fully loaded condition where all the rollers are in contact or in the fully open position. The device shown in the aforementioned patent disclosure, however, does not provide for a partial load condition wherein the contacting pressure is removed from the rollers. Such a partial load condition is desirable during short periods in which the machine may be shut-down for adjustment or repair. It is preferable that the last pair of rollers in the direction of yarn movement (i.e. the front most pair of rollers) remain in contact under a small amount of pressure holding the yarn so that the yarn does not unravel and so that the twist imparted to it is not lost. Simultaneously the remaining rollers are placed out of contact with each other to avoid deformation of the roller bodies and/or the slivers under the high operating pressures.

It is an object of the present invention to provide apparatus for carrying and loading top-rollers which overcomes the defects of the prior art.

It is another object of the present invention to provide apparatus for carrying and loading top-rollers capable of being placed in a partial load condition.

It is another object of this invention to provide apparatus for carrying and loading top rollers which can be placed in a partial load condition where the front rollers remain in contact at a pressure only a fraction of the operating pressure.

It is another object to provide apparatus for carrying and loading top rollers wherein the full, partial, and open load positions are well defined and tactually apparent during operation.

These objects, others, as well as numerous advantages will be apparent from the following description of the present invention.

SUMMARY OF THE INVENTION According to the present invention the top-rollers are carried on a carrier arm which is interconnected with an operating lever. The carrier arm and operating lever are mounted about a common stationary shaft secured in a support housing. Means fixed to the support housing is located exteriorly of carrier arm and positioned to engage with the carrier arm. The stationary shaft and the fixed means comprising two points by which the pivoting movement of the carrier arm is determined whereby the carrier arm may be selectively placed in a fully closed, partially closed, and open position.

Preferably the carrier arm is provided with a cam in the form of a plate at its rear end which has at least a portion of its perimeter contoured and engaging with the fixed means forming the second point and cooperating therewith to form a cam surface for lifting and moving the carrier arm. In an alternative embodiment an arm having a contoured edge is mounted about the fixed means forming the second point. The contoured edge of the arm comprising a cam surface for the same purpose.

According to the present invention the operating lever and the carrier arm is interconnected by an overthe-center crank arrangement which provides a positive torque necessary to achieve the desired pressure contact of the rollers in the closed position. The interconnecting means further includes linkages for defining the various closed partial load and open position.

Full details of the present invention will be seen in the accompanying drawings and in the following description.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings:

FIG. 1 is a side elevational view of a carrier arm, operating lever, and support in closed position with the rollers in full contact;

FIG. 2 is a view. similar to FIG. 1 showing the partial load condition;

FIG. 3 is an enlarged detailed view of the mechanism for supporting the carrier arm and lever in closed condition in partial section along line 3-3 of FIG. 4;

FIG. 4 is a sectional view of the mechanism along line 4-4 of FIG. 3;

FIG. 5 is a view similar to FIG. 3 showing the mechanism in partial load condition;

FIG. 6 is a view similar to FIGS. 3 and 5 showing the mechanism in fully open condition; and v FIG. 7 is a view similar to that of FIG. 3 showing the alternate embodiment of the present invention.

DESCRIPTION OF THE INVENTION As seen in FIG. 1 the carrier arm is supported in a housing 12 open on one side. The housing 12 has sides mounted on a shaft or bar 10 fixed to the machine frame. A carrier arm 14 to which is operatively connected an operating lever 16 is pivotally mounted in the support 12 The carrier arm 14 is provided with a plurality of links or retaining means 18 having saddles in which the top rollers 20 are secured. A form of such link can be seen in, and reference made to the copending application of Franz Fuchs, Ser. No. 120,535 filed March 3, 1971, now U.S. Pat. No. 3,722,036, based upon German Application No. P 20 10 104.6 filed March 4, 1970 and assigned to the present assignee. Opposed to each of the top rollers 20 are bottom rollers 22 supported on the machine frame. The link mechanism 18, top rollers 20 and bottom rollers 22 are constructed and arranged in conventional manner to provide a well known three stage yarn twisting mechanism in which the sliver is moved between the horizontal plane defined between the roller faces Reference to conventional details of carrier arm construction or to other constructions can be made to the aforementioned German Patetn Disclosure, German Patent No. 1,088,850 and U. S. Pat. No. 3,212,139, as well as to the copending application of Franz Brichta and Franz Driesel Ser. No. 121,719 filed Mar. 8, 1971, now US. Pat. No. 3,740,798, which is based on German Application P 20 11 641.0 filed Mar. 12, 1970 nd. 3 Si ld.. F9lll PLPL% MM FIG. 1 illustrates the operating position of the present twisting device wherein all of the top rollers 20 are substantially equally pressed with considerable force (in the range of about 30 K against their associated lower rollers. In FIG. 2, on the other hand, the carrier is shown in partial load condition, where only the forwardmost (as seen in the figure, the leftmost top roller) is pressed against its associated roller. In this condition the pressure on the rollers is considerably less than in the operating condition, being sufficient merely to hold the yarn and prevent it from losing hold of or permitting unravelling of the twist imparted to the fiber slivers.

The details of the present mechanism are seen in FIGS. 3 and 4. The carrier arm 14 is in cross section a U-shaped channel member having spaced sides enclosing the roller links. The inner end of the carrier arm 14 is secured to a pair of spaced removable bolts 24 to which is also secured a contoured cam 28 which comprises two plates fixed between the sides of the carrier arm 14 and spaced from them by spacers or washers 26. This separable construction of carrier arm 14 and cam 28 is desireable because it affords considerable ease in manufacture and assembly; however, the cam may be unitarily formed or otherwise secured with the arm, if it is so desired. It will also be noted from FIG. 4, that many of the elements of the mechanism are supplied in duplicate and symmetrically arranged to either side of the central vertical plane passing through the support housing 12. Although such parts may be duplicates they may be thought of and so described in structure and function as only unitary members.

The cam 28 has a compound shape similar more or less to a distorted keystone. Its operative cam face 28a is located along its lower left hand edge and is a wide mouth U-shaped curve extending at its lowermost portion in a slightly 'arcuate section terminating from a sharp point 280 midway therealong. A dog-legged cam opening or slot 28b is formed in the central portion of the plates.

Two stationary or fixed pins 30 and 32 are secured transversely across the sides of the supporting housing 12 and carry a sleeve 34 and a split sleeve 36 respectively. The inner diameter of the split sleeves 36 is substantially larger than the outer diameter of the pin 32 on which it is joumalled, enabling the sleeves to move radially with respect to the pin 32 as well as to rotate about it. The pin 30 and its sleeve 34 pass through aligned slots 38 formed in each of the plates of the cam 28 and the inner end of the carrier arm 14 between the removable bolts 24. The split sleeve 36 is located opposite the operating cam face 28a. Both the slot 38 and the cam face 28a are inclined to the vertical, as seen in FIG. 4, although the cam face 28a is at a smaller angle than the slot 28b.

The shaft 10, on which the support housing 12 is secured, is provided with a plurality of longitudinal coglike lands and valleys a. Fastened between the sides of the support 12 are spaced adjusting plates between which an adjusting nut 12b inclined to the vertical is securely fixed. An adjusting screw 12c threadedly passes through the nut 12b. The plates 12:: have a slot inclined to the horizontal and aligned with the end of the adjusting screw 12c. A fixing nut 12c passes through this slot and is securedly fixed to the sides of the support housing 12. A fixing screw 12d threadedly passes through the nut 12:: so that its end is adapted to engage the lands 10a. The end of the adjusting screw 12c engages the fixing nut l2e. Adjustment of both or either of screws 12c or 12d permits the gross location of the support housing about the support shaft 10.

Fixedly mounted to the fixing nut 12e is one end of a leaf spring 40 which extends in a curved hairpin manner between the disks 12a about the shaft 10. The free end of the hairpin shaped leaf spring 40 is curved into a saddle shape and abuts against the sleeves 36 mounted about the pin 32.

Between the cam surface 28a and the forward retaining pin 24, the plates of the cam 28 bulge outwardly and carry a stop pin 42 about which is joumalled a sleeve 44. A similar pin 46 without a sleeve is located between the plates of the cam 28 somewhat offset to the right of a line between the cam surface 28a and the rear retaining pin 24.

The upper stationary pin 30 serves to support the operating lever 16, through a T-shaped bifurcated lug 16a which straddles the plates of cam 28 and which is pivotally secured to the pin 30. The lug 16a extends downwardly beyond the pin 30 and carries transversely between its ends a coupling pin 16b journalling a coupling sleeve 16c between the sides of the lug 16a. The coupling sleeve 16c passes through the dog-legged slot 28b in the plates of the cam 28. The upper end of the long portion of the dog-leg slot 28b is contoured and positioned to the right beyond the line connecting the fixed pins 30 and 32 while the shorter dog-leg portion is directed downwardly and then upwardly to the other side of the connecting line. This enables the coupling pin 16b to take an arcuate path about the fixed pin 30 on movement of the operating lever 16 and to create an over-the-center crank mechanism which produces a positive pressure force upwardly against the rear of the carrier arm resulting in the creation of the 50 K, force on the rollers.

Located between the plates of the cam 28 is an elongated contoured link 50 pivotally secured at its lower end about pin 32 and extending upwardly toward the upper pin 30. The link 50 is provided with a curved slot 50a through which the coupling pin and sleeve 16b and 16c respectively, also pass. The link 50 is provided, further, with a cam edge 50b on its left or forward side terminating at its upper end in depression or hook seat 50c which is adapted to cooperate with the stop sleeve 44. A locking spring 52 is turned in a tight U-shape about one part of the split roller 36 and has one end abutting against the sleeves 16b of the operating arm lug 16a and its other arm abutting against the pin 46.

The aforedescribed embodiment functions in the following manner:

When the mechanism is placed in the operating position seen in FIGS. 1 and 3, the operating lever 16 is closed so that all the associated rollers 20 and 22 are in pressure contact. The cam face 280 and the upper edge of the slot 38 are engaged by their associated fixed pins and sleeves 32, 36 and 30, 34 respectively. Moreover, the transverse coupling sleeve 160 at the end of the operating lug 16a is in contact with the upper or extreme end of the long portion of the dog-legged slot 28b. This outer end of the slot 28b is, as is seen from FIG. 5 and 6, provided with an angled or elbowed portion, the edge of which forms a reference or dead center line against which the roller 16c is adapted to lie. This edge forms, relative to a line through the shaft 30 and the pin 16b, an angle, the apex of which provides a center stop position for the pin and thus a temporary latching point for the cam 28 and the arm 14 carried by it when in the partially open position. Because of the shape of the slot 28b, the coupling pin 16b is located to right of the reference or dead center line forcing the rear end of the carrier arm 14 upwardly about the fixed pivot pin 30 and thus the front portion of the carrier arm 14 downwardly so that the rollers 20 and 22 are in contact. By predetermining the arrangement described a force of about 50 K can be exerted by the rollers 20 on rollers 22. The leaf spring 40 continually presses the split sleeves 36 against the stationary pin 32 on which it journalled and against the cam face 28a urging the carrier arm into closed condition. In this position the link 50 has no function at all, remaining slack about the coupling sleeve 16c.

To assume the partial load position, the operating lever 16 is pivoted upwardly, as seen in FIG. 5, so that the carrier arm 14 is lifted, as seen in FIG. 2 to where only the extreme outward rollers 20 and 22 are in contact with only enough pressure to hold the yarn. The partial load position is tactually sensed when the mechanism reaches a defined holding point in the manner to be described.

As the operating lever 16 is moved upwardly the control sleeve 16c abutting against the upper end of the slot 28b, is caused to lift the cam 28 until the sleeve 34 surrounding the pin 30 hits the bottom end of the slot 38. The carrier arm is forced in a slight counterclockwise arcuate movement about its frontmost top roller. The rear rollers are thus lifted from contact with their associated bottom rollers (FIG. 2.) Simultaneously, the control sleeve pivots the link 50 in a counter-clockwise manner until it abuts against the sleeve 44 surrounding the stop pin 42. In this position the leaf spring 40 causes the sleeves 36 to engage the sharp tip 280 of cam 28 forcing the cam 28 upwardly in a direction to the right hand corner of the device, (FIG. 5). The release of the operating lever 16 and the movement of the control sleeve 160 in the dog-leg slot 28b breaks the over-the-center crank and the pressure on the cooperating top and bottom rollers 20 and 22 is removed. Nevertheless, the leaf spring 40 is of sufficient strength to urge the cam 28 upward (through action of the sleeve 36 on the point 280) sufficient to cause at least a 5 K, force on the frontmost rollers, thereby securely holding the yarn. As is evident from FIG. 5, the control sleeve 16 has meanwhile moved downwardly in a clockwise arcuate direction into the corner of the dog-leg slot 28b which together with the action of the link 50 against the sleeve 44, establishes the tactile definition of this partial load position.

The arrangement thus described for establishing a partial load position is effective even if the frontmost top roller is somewhat reduced in diameter due to wear. The spring leaf 40 urges the rear of the cam upwardly with sufficient force to compensate for normal wear of the roller.

When it is intended to disengage the rollers 20 and 22 completely, the operating lever 16 is pivoted clockwise even further. This additional movement of the lever 16 causes the control sleeve 16c to push the link 50 to the left against the sleeve 44 surrounding the stop pin 42. This causes the control sleeve 16c to enter into the upward small portion of the dog-leg slot 28b, as seen in FIG. 6. This exerts an upward force on the cam 28 to the right of the dead center line lifting the cam 28 about the fixed pivot pin 30, swinging the carrier arm 14 with it. The top pin 42 is thus moved to the left permitting the link 50 to swing still further counterclockwise until its hook portion 50c engages the sleeve 44 which then seats therein. The carrier arm 14 thereby becomes locked in its extreme open position.

In this locked position the control sleeve is abutting with the upper end of the link slot 50a and the end of the short dog-leg portion. The arresting spring 52, wound about the split sleeve 36, urges the control sleeve 16c to the left maintaining the operating lever lug 16a in that direction. Also the spring 52 urges the link 50 against the sleeve 44 which is seated in the depression 50c. Simultaneously, the extreme outer end 28d of the cam surface seats on the sleeve 36 urging the cam 28 upward to the left. This maintains the locked position of the carrier arm 14 in extreme open position even against the counter-clockwise torque exerted by its own weight. In order to define a specifically fixed terminal position in the extreme open condition, so that the carrier 14 is not pivoted too far, the inner-surfaces of the support housing 12 are provided with embossed or punched inwardly extending stop means 12f. On clockwise movement of cam 28 the stop pin 46 is adapted to abut against the stop means 12f when the open position is reached.

When the carrier arm 14 is to be again placed in its operative position, the operating lever is pressed downwardly counter-clockwise. The force of the downward movement overcomes the biasing of the arresting spring 52 and permits the control sleeve 160 to move in the slots 28b and 50c. This causes the link 50 to pivot and swing to the right releasing the sleeve 44 from the seat 50c. The cam 28 and the carrier arm is then permitted to swing counter-clockwise. The control sleeve 16c rides in the cam like surfaces of the slot 28b, the external cam surface 28a again rides on the sleeve 36 and the sleeve 34 rides in slot 38. Thus the cam 28 swings between the two fixed points created by the pins 30 and 32 until the control sleeve 16c again passes the dead center line and forces the carrier arm 14 into its pressured operating position, as seen in FIG. 3.

Because of the relative inclinations of the slot 38 and the cam slot 28a, which are deliverately predetermined, a differential in pivoting movement is created wherein the carrier arm 14 is moved at its rearward or support end more than at its forward roller carrying end. This is essential in order to achieve the positive partial load position without loss of the yarn on upward movement, and to close all the rollers, on downward movement, before full pressure is applied. The entire operation, i.e., the entire manipulation of the carrier cam can be obtained through the operators use of only one hand.

A modified version of the apparatus is shown in FIG. 7. In this embodiment the split sleeves 36 are replaced with an elongated contoured cam lever 60 and the leaf spring 40 is replaced by a tension spring 62. The lever is provided with a rectangular slot 66 through which the pin 32 passes. The lever 60 is pivoted at its left or upper end about a bolt 64 secured to the support housing 12 and is connected at its other end to the tension spring 62 which is also fastened to the support housing. The spring 62 normally biases the lever upwardly toward the upper right hand corner. The lever 60 has an angular cam surface 68 which engages with a roller cam follower 28c passing through the plates of the cam 28 adjacent the cam surface 28a and 28b. Otherwise the mechanism is constructed in the same manner as the embodiment shown in FIGS. 1-6 and similar parts are denoted by similar reference numerals.

The device shown in FIG. 7 operates in a similar manner as that shown in FIGS. 1-6; the fully loaded or closed position being the same as seen in FIG. 3. However, the partial load position is effected by engagement of the high point of the cam surface 68 with the roller 280' which in this embodiment serves as the full functional equivalent of the corner projection 280 of the earlier embodiment. Thus, in combination, cam surface 68 and follower 28c replaces the action of cam surfaces 28a and 28c and the sleeve 36. The tension spring 62 can obviously be replaced by a compression spring of suitable design.

The position of the cam follower 28c is shown in three positions in FIG. 7, corresponding to the positions assumed during manipulation. The full line position denoted by the numeral I is indicative of its position when the carrier arm is fully closed and operative; numeral II is indicative of the position assumed by the follower 280' (in dotted lines) in the partial load condition; and; III is indicative of the position of follower 280' (also in dotted lines) in the fully open condition. It will also be clear that the cam 28, arm 14, lever 16 as well as all the other mechanism moves, as previously described, into corresponding positions even though not shown in FIG. 7, in dotted lines.

It will thus be seen that the apparatus provides two fixed points which define the movement of the carrier arm and a cam action by which the rear end of the carrier arm is lifted, without lifting the forwardmost roller to provide the partial load contition. To achieve the partial load condition each of the points have associated therewith a cam surface or track provided by the slot 38 and cam face 28a respectively. The cam tracks are oriented at different angles to provide a differential angle so that an upward movement in response to the pivoting action of the operating lever causes the rear end of the carrier arm to be moved a greater distance than the front end. The provision of one of the points interiorly of the carrier arm and the other point exteriorly thereof, permits the carrier arm to be lifted into its partial load position and held securely therein until further operation of the operating lever. The interior fixed point represented by roller 34 rests, during partial load position, on the bottom of cam slot 38, while the exterior point represented by the shaft 32 is urged upwardly against the high point 28c or 280 of the cam surface. In this manner the carrier arm can not be shifted without movement of the coupling elements 160 through the lever 16. Thus the partial load position is positively obtained and tactually sensed and also securely held so that the operator need not continue to holdthe operating lever. The operator is thus free to make any adjustment or repair necessary.

Another advantage is obtained by the arrangement described in that a small closing force is required to re lease the stop 44 from the seat 500 of the operating link 50. A positive closed position with full pressure on the rollers is also advantageously obtained by the over the center crank arrangement provided by the construction shown. Only a very small force is required to overcome friction and force the carrier arm closed.

The provision of the spring 40 or 62 creates a positive torque or movement on the carrier arm insuring positive engagement of the rollers in open or closed position.

Various modifications and changes have been suggested herein. Other modifications will be readily apparent to those skilled in this art. It is, therefore, to be understood that the description is to be taken as illustrative only and not limiting of the present invention.

What is claimed:

1. In a sliver drawing and spinning mechanism having at least two pairs of top and bottom rollers aligned for drawing slivers therethrough, apparatus for carrying the top rollers and for pressing the top rollers during operation into contact with their corresponding bottom rollers, comprising a stationary support, a top roller carrier arm having a cam member at its rearmost end, the cam end of said arm being mounted in said support to swing about a first fixed element and to slidingly engage with a second fixed element exterior thereof, an operating lever connected to said arm and having a lug depending therefrom adjacent said cam end, a link mounted in said support to swing about said second fixed element, and means for coupling said lever, carrier arm and link, said coupling means comprising a first slot formed in said cam member, a second slot formed in the link and a coupling pin secured to the lug of said lever and extending transversely into said first and second slots, said first and second fixed elements being oriented so that the arm may be selectively moved, so that in the operating position of said arm both said fixed elements and said lug absorb the forces created by the contact of all of said top and bottom rollers and act to create a pressure moment on said arm to bias the same in the closing direction; the arm may be swung by said lever so that said fixed elements and said link cooperate to lift said arm at its rearmost end into a partially open position wherein the top rollers at the rearmost end of the arm are out of contact with the corresponding bottom rollers while the top and bottom rollers at the forward end of the arm remain in contact; and the arm may be further swung into a fully open position wherein said fixed elements and link cooperate to lift said arm so that all said rollers are out of contact, said first slot being so angled so as to provide a first portion in which said pin is held to define the limits of the partially open position and a second portion in which said pin is held to define the limits of the fully open portion.

2. The mechanism according to claim 1, wherein said cam member has an extending stop member and said second fixed element is provided with a spring, said spring bearing against said link to urge said link into engagement with said stop member to resiliently hold said pin in said stop positions.

3. The mechanism according to claim 2 wherein said first and second fixed elements are aligned with respect to the lever and the coupling means so that said coupling means and lever move cooperatively to provide an over the center crank.

4. The mechanism according to claim 2 wherein the link is provided with two cam edges, one of which is formed by said second slot and engages the coupling pin, the other of which is formed by an exterior edge adapted to engage said stop member secured to said cam member during partial opening.

5. The mechanism according to claim 4 wherein said other cam edge has a notched portion in which said stop member is adapted to seat during full opening.

6. The mechanism according to claim 2 wherein the first fixed element comprises a fixed shaft extending through a slot formed in the cam end of said carrier arm and the second fixed element comprises a roller journalled about a fixed shaft, said roller having an enlarged inner diameter to permit a degree of radial play about the shaft.

7. The mechanism according to claim 2 wherein said link comprises an elongated bracket pivotally secured at one end to said support and said second slot has a cam edge adapted to engage said coupling pin said slot permitting transverse shifting of said arm with respect to said second fixed element, and said spring means normally urges said bracket into contact with said coupling pin, said cam edge being contoured and contacting said coupling pin to thereby resiliently bias said car- 

1. In a sliver drawing and spinning mechanism having at least two pairs of top and bottom rollers aligned for drawing slivers therethrough, apparatus for carrying the top rollers and for pressing the top rollers during operation into contact with their corresponding bottom rollers, comprising a stationary support, a top roller carrier arm having a cam member at its rearmost end, the cam end of said arm being mounted in said support to swing about a first fixed element and to slidingly engage with a second fixed element exterior thereof, an operating lever connected to said arm and having a lug depending therefrom adjacent said cam end, a link mounted in said support to swing about said second fixed element, and means for coupling said lever, carrier arm and link, said coupling means comprising a first slot formed in said cam member, a second slot formed in the link and a coupling pin secured to the lug of said lever and extending transversely into said first and second slots, said first and second fixed elements being oriented so that the arm may be selectively moved, so that in the operating position of said arm both said fixed elements and said lug absorb the forces created by the contact of all of said top and bottom rollers and act to create a pressure moment on said arm to bias the same in the closing direction; the arm may be swung by said lever so that said fixed elements and said link cooperate to lift said arm at its rearmost end into a partially open position wherein the top rollers at the rearmost end of the arm are out of contact with the corresponding bottom rollers while the top and bottom rollers at the forward end of the arm remain in contact; and the arm may be further swung into a fully open position wherein said fixed elements and link cooperate to lift said arm so that all said rollers are out of contact, said first slot being so angled so as to provide a first portion in which said pin is held to define the limits of the partially open position and a second portion in which said pin is held to define the limits of the fully open portion.
 2. The mechanism according to claim 1, wherein said cam member has an extending stop member and said second fixed element is provided with a spring, said spring bearing against said link to urge said link into engagement with said stop member to resiliently hold said pin in said stop positions.
 3. The mechanism according to claim 2 wherein said first and second fixed elements are aligned with respect to the lever and the coupling means so that said coupling means and lever move cooperatively to provide an over the center crank.
 4. The mechanism according to claim 2 wherein the link is provided with two cam edges, one of which is formed by said second slot and engages the coupling pin, the other of which is formed by an exterior edge adapted to engage said stop member secured to said cam member during partial opening.
 5. The mechanism according to claim 4 wherein said other cam edge has a notched portion in which said stop member is adapted to seat during full opening.
 6. The mechanism according to claim 2 wherein the first fixed element comprises a fixed shaft extending through a slot formed in the cam end of said carrier arm and the second fixed element comprises a roller journalled about a fixed shaft, said roller having an enlarged inner diameter to permit a degree of radial play about the shaft.
 7. The mechanism according to claim 2 wherein said link comprises an elongated bracket pivotally secured at one end to said support and said second slot has a cam edge adapted to engage said coupling pin said slot permitting transverse shifting of said arm with respect to said second fixed element, and said spring means normally urges said bracket into contact with said coupling pin, said cam edge being contoured and contacting said coupling pin to thereby resiliently bias said carrier arm during said shifting. 